Polyamide (PA) is a group of important polymers that are used as raw materials for a series of special plastics to be used in the automobile industry, sports industry and lifestyle industry, and diamines are important raw material monomer components for the polyamides. Diamines are condensed with dicarboxylic acids to form various polymers, and the properties of the polymers vary depending on the chain lengths of the diamines and the dicarboxylic acids.
Conventionally, diamines are chemically produced from materials derived from petroleum via dicarboxylic acids at an intermediate stage, or produced by chemical decarboxylation reaction of amino acids Suyama and Kaneo. Yakugaku Zasshi (1965), Vol. 85, pp. 513-533. In consideration of sharp rise in oil prices, the methods of synthesis of diamines are preferably switched to methods based on biotechnological processes such as enzyme reactions and microorganism culture, wherein renewable resources are utilized.
In view of this, recent interest has focused on cadaverine as a diamine which can be produced by biotechnological processes. Cadaverine is also called 1,5-pentanediamine, and is a compound that can be a raw material monomer for polyamide. Cadaverine is a biogenic amine which ubiquitously exists in the living body and its biosynthetic system is being elucidated (see Celia White Tabor and a colleague. Microbiological Reviews (1985), Vol. 49, pp. 81-99). In a part of its biosynthetic pathway, lysine decarboxylase (LDC) that catalyzes decarboxylation of lysine into cadaverine is known to be involved. As an LDC gene, the E. coli (Escherichia coli)-derived LDC gene is known (see Shi-Yuan Meng and a colleague. Journal of Bacteriology (1992), Vol. 174, pp. 2659-2669).
The conventional biotechnological methods for producing cadaverine are based on introduction of an LDC gene into a microorganism, and can be roughly classified into production methods by enzyme reaction using lysine as a substrate and methods for producing cadaverine by microorganism culture. Further, known examples of the methods for producing cadaverine by microorganism culture include a production method by culturing recombinant E. coli (see JP 2002-223770 A), a method wherein the capacity of a coryneform bacterium, which is a lysine-producing microorganism, to produce lysine is further enhanced (see JP 2004-222569 A), a method wherein the cadaverine degradation system is blocked (see Japanese Translated PCT Patent Application Laid-open No. 2009-531042) and a method wherein the lysine transporter is blocked (see WO 2008/092720). However, there are many problems to be solved especially in the methods for producing cadaverine by microorganism culture, and examples of such problems include by-production of lysine in cases of culture of a microorganism prepared by introduction of an LDC gene to a coryneform bacterium, which is a lysine-producing microorganism (see Takashi Mimitsuka and four colleagues. Bioscience, Biotechnology, and Biochemistry (2007), Vol. 71, pp. 2130-2135). By-production of lysine prevents improvement of the yield of cadaverine even with successful production of its precursor. Further, since cadaverine needs to be highly purified in order to be used as a raw material for polyamide, By-production of lysine increases the load on purification of cadaverine, which has been economically problematic.
It could therefore be helpful to provide a method for producing cadaverine by culturing a microorganism, which method does not allow lysine as a precursor of cadaverine to remain in the microorganism culture liquid upon completion of culturing of the microorganism.